21506956800 has 960 divisors, whose sum is σ = 87680102400. Its totient is φ = 4541644800.

The previous prime is 21506956799. The next prime is 21506956847. The reversal of 21506956800 is 865960512.

It is a tau number, because it is divible by the number of its divisors (960).

It is a Harshad number since it is a multiple of its sum of digits (42).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 95 ways as a sum of consecutive naturals, for example, 241651156 + ... + 241651244.

It is an arithmetic number, because the mean of its divisors is an integer number (91333440).

Almost surely, 2^21506956800 is an apocalyptic number.

21506956800 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21506956800, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (43840051200).

21506956800 is an abundant number, since it is smaller than the sum of its proper divisors (66173145600).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21506956800 is a wasteful number, since it uses less digits than its factorization.

21506956800 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 187 (or 166 counting only the distinct ones).

The product of its (nonzero) digits is 129600, while the sum is 42.

The spelling of 21506956800 in words is "twenty-one billion, five hundred six million, nine hundred fifty-six thousand, eight hundred".